This invention is generally directed to a novel door lock mechanism for use with a semi-trailer.
A conventional tractor 10 and trailer 12 (also commonly referred to as a “semi-trailer”) are illustrated in FIG. 1. Specifically, the trailer 12 is shown connected to the tractor 10. The trailer 12 includes a floor 14 with an undercarriage assembly 16 thereunder at its rearward end and an extendable and retractable landing gear assembly 18 thereunder positioned approximately half way between the front end of the trailer 12 and the trailer's longitudinal center of gravity. Opposite side walls 20 and a front wall 22 extend upwardly from the floor 14. A roof 24 is provided to close the top of the trailer 12. The roof 24 is secured to the side walls 20 by metal top rails 23, and the floor 14 is secured to the side walls 20 by metal base rails 25.
As illustrated in FIG. 2, a pair of rear doors 26 are provided at the rear end of the trailer 12 and are hingedly mounted to a rectangular rear frame 28 which has a rectangular opening therethrough into which the rear doors 26 fit when the rear doors 26 are moved to the closed position. The rear frame 28 includes a base portion 29 which is below the rear doors 26. FIG. 2 shows conventional door lock mechanisms 30 that are typically provided on the rear doors 26. Typically, the right door is referred to as the “curbside” door and the door lock mechanism associated therewith is referred to as the “curbside” lock. Likewise, typically the left door is referred to as the “roadside” door and the door lock mechanism associated therewith is referred to as the “roadside” lock.
Each door lock mechanism 30 includes an elongated, cylindrical lockrod 32 which extends along the height of the respective rear door 26. A generally U-shaped bearing plate 34 is provided proximate each end of the lockrod 32 and the bearing plates 34 are secured to the rear door 26 by fasteners 36. The lockrod 32 rotates within the bearing plates 34, and a handle 38 is provided for manipulating the position of the lockrod 32. As shown, the handle 38 is provided partway up the lockrod 32, on the respective door 26.
A cam 40 is integrally formed at each end of the lockrod 32. Each cam 40 is configured to engage corresponding keeper structure on the trailer, thereby locking the doors in the closed position. Specifically, the cams 40 at the bottom of the lockrods 32 engage lower door lockrod keepers 42, which are mounted on the rear frame 28, below the door opening. The cams 40 at the top of the lockrods 32 engage upper door lockrod keepers 44, which are mounted on the rear frame 28, above the door opening. Each keeper 42, 44 is attached to the rear frame 28 by suitable means, such as a weldment. As shown in FIG. 2, brackets 46 are typically provided on the doors 26 for engaging and securing the handles 38. Although not shown in FIG. 2, typically the brackets 46 are configured such that padlocks can be engaged with the brackets 46, thereby locking the handles 38 in place on the doors 26 (and thereby locking the doors 26 in the closed position).
As discussed above, door lock mechanisms 30 which are typically used in association with the rear doors 26 of a trailer 12 include bearing plates 34 which are secured to the doors 26, generally proximate each end of the lockrods 32. As shown in FIG. 2, the bearing plates 34 do not extend the entire height of each door 26. As such, the bearing plates 34 provide limited support for the lockrods 32.
As discussed above, door lock mechanisms 30 which are typically used in association with the rear doors 26 of a trailer 12 provide cams 40 at the top and bottom of the lockrods 32 which engage keepers 42, 44 on the trailer 12, and the brackets 46 are used to secure the handles 38. Typically, there is no other mechanism provided for locking the handles 38 in place other than the brackets 46 on the doors 26. Door lock mechanisms 30 which are typically used in association with the rear doors 26 of a trailer 12 also do not provide that the doors 26 can be secured in an open position. Additionally, because the handles 38 are provided partway up the doors 26, when the doors 26 are swung to the open position, the handles 38 may bear against the side walls 20 of the trailer 12, possibly causing damage.
The present invention provides a novel locking mechanism which overcomes the disadvantages presented by the prior art. Other features and advantages will become apparent upon a reading of the attached specification, in combination with a study of the drawings.